What this error means
Heating circuit fault — the dishwasher is not heating water to the required temperature during a wash cycle.
The E09 error on a Bosch dishwasher means the machine has detected a problem with its heating circuit. Bosch dishwashers monitor water temperature throughout every heated programme and will display E09 if the water fails to reach the target temperature within the expected time, or if the temperature sensor returns a reading that is inconsistent with normal heating. The most common causes are a failed heating element or flow heater, a faulty NTC temperature sensor, heavy limescale coating on the heating element reducing heat transfer efficiency, or a wiring fault to either component. On many Bosch models the heating element takes the form of a flow-through heater rather than a conventional immersion element.
Also known as: Same as Siemens & Neff E09
What you'll need first
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Step-by-step
Symptoms to look for
- E09 displayed partway through a wash programme, typically during the main wash or rinse phase
- Dishes coming out cold or insufficiently cleaned after a heated programme
- Dishwasher takes significantly longer than the displayed time estimate on programmes above 50 degrees
- E09 appears consistently on high-temperature programmes but not on cold rinse cycles
Diagnostic steps
Add a proprietary dishwasher descaler or citric acid equivalent to the base of the empty tub and run a 65-degree cycle with no dishes or detergent. In hard water areas limescale builds up on the heating element or flow heater surface over time, acting as an insulating layer. The heater draws full electrical power but transfers very little to the water — the control board detects slow temperature rise and displays E09. Descaling resolves many E09 faults without any part replacement.
Unplug the machine and hold the power button for 10 seconds. Leave unplugged for five minutes. Plug back in and run a 65-degree programme. Monitor whether E09 reappears.
With the machine completely unplugged, remove the lower kickplate panel and the inner base cover to access the underside of the tub. The NTC thermistor on most Bosch dishwashers is a small cylindrical sensor mounted to the flow heater body or to the tub base near the heater outlet. It connects to the wiring harness via a two-pin connector.
Disconnect the NTC two-pin connector from the wiring harness. Set a multimeter to resistance mode and test across both sensor terminals. At room temperature of approximately 20 degrees Celsius a healthy Bosch NTC thermistor typically reads between 10,000 and 50,000 ohms depending on the model. A reading of zero indicates a short circuit inside the sensor. A reading of OL means the sensor has failed with an open internal circuit. Either reading will produce E09.
With the machine unplugged, disconnect the wiring from the heater terminals. Set a multimeter to resistance mode and test across the heater terminals. A functional Bosch dishwasher heating element or flow heater typically reads between 15 and 40 ohms depending on its wattage rating. A reading of OL indicates an internal open circuit and the heater has failed. A reading of zero or near zero indicates a short circuit.
With the machine unplugged, inspect the wiring harness between the control board and the heater. Check for sections that are chafed, pinched, burnt, or showing discolouration of the insulation. Disconnect and firmly reseat the wiring connector at the heater end.
When to call an engineer
- Heating element or flow heater reads open circuit or short circuit on a multimeter — heater must be replaced before use
- Earth fault confirmed between a heater terminal and the machine earth point — do not use the machine under any circumstances until repaired
- NTC thermistor reads outside the expected resistance range or fluctuates when its leads are gently flexed — sensor must be replaced
- Heater and sensor both test within normal range but E09 persists on every heated cycle — control board heating input circuit fault requiring specialist diagnosis
Frequently asked questions
What is the flow heater on a Bosch dishwasher and how does it relate to E09?
Can limescale cause E09 on a Bosch dishwasher?
Is it the heater or the sensor that has failed when E09 appears?
Can E09 appear even if the water is actually warming up?
This video shows you how to replace the heat pump on a Bosch, Siemens or Neff Dishwasher
- Accessing the pump
- Removing the cables
- Removal and installation of the heat pump
🎯 What is likely causing this fault?
⚠️ Estimates based on common faults — not a guaranteed diagnosis. Always verify before ordering parts.
Parts you may need
Enter your model number to filter results to your exact machine
Usually found on a label inside the door frame or on the back panel of the machine.
| Part | Approx. UK Cost | Find it |
|---|---|---|
| Heat Pump | £100 - £150 | 🛒 Amazon UK → |
| Heat Pump | £90 - £120 | 🏷️ eBay UK → |
| Multimeter | £10 - £20 | 🛒 Amazon UK → |
ℹ️ Prices are approximate. Always check the part number matches your model before ordering. Not sure of your model number? Find out how to locate it here.